pfinstall enables you to test a profile against:
The system's disk configuration where pfinstall is being run.
Other disk configurations by using a disk configuration file that represents a structure of a disk (for example, a disk's bytes/sector, flags, slices). Creating disk configuration files is described in:
You cannot use a disk configuration file to test a profile you intend to use to upgrade a system. Instead, you must test the profile against the system's actual disk configuration and the software currently installed on that system.